Laterally sliding roller ski

ABSTRACT

A roller ski allowing the skier to slide laterally in a manner similar to a snow ski. The system includes at least one ski and it would attach one foot per ski. Each ski has an optionally height and longitudinal angularly adjustable center platform for fixturing the skier&#39;s foot with an optionally releasable ski binding system, an optionally height and longitudinal angularly adjustable front tip and rear tail for attaching at least four fixed wheels, and at least two biased pivoting casters which are all positioned along the center platform&#39;s longitudinal axis. The fixed wheels function similarly to conventional roller skate trucks. The casters rotate to align themselves with the direction of force exerted on the center platform. The casters are spring biased to align them selves with the longitudinal axis of the center platform. A height differential between the wheels and rollers enables the skier to transfer weight from one to the other, alternating between the carving and sliding characteristics of snow skis. Another option is at least one ski pole for increased ease of skier balance and self propulsion, with modified tips to accommodate more surfaces than just snow.

BACKGROUND OF THE INVENTION

This invention relates to a roller ski, specifically to one that can transition in and out of a mode of controlled omnidirectional motion, and be able to stop on inclined surfaces, in a manner similar to the behavior of a snow ski.

Throughout roller skiing's history, which dates back to the 1930's, the basic configuration of equipment has been consistent: skis, single axis rotational wheels, some form of fixturing the wheels, an optional mechanical braking system and some form of restraining the skier's feet. Product advances have always occurred in the context of this basic configuration. Improvements in wheel, bearing and ski material and skier foot fixturing have been made but the essential functionality of the skis nor their motion characteristics have been changed. During the history of roller skiing, snow skiing has also existed and grown in popularity. The market desired lateral motion experienced during snow skiing result from complex interactions between the skier, ski and snow conditions. To simplify, two general motion characteristics can be readily identified and these are described below. Many of these motions are common to the water sport known as water skiing. The discussion below limits itself to snow skiing because of its direct similarities to roller skiing.

First, a snow skier can turn by shifting their weight and rotating their body to determine direction of travel. This effect results from the presence of side cut and flex in the ski design. As the ski leans onto its edge, it turns an arc equivalent to the radius of the ski's edge. If this type of turn is executed cleanly, it is referred to as “carving” and involves little or no lateral slippage of the ski or skier. The skier can control the severity of the turn radius by transferring more or less weight. Roller skates have long replicated this turning behavior through the mechanical design of roller skate trucks. The truck's simple design turns the skate through gentle or severe turns depending on the amount of weight shift, lateral leg input, and body rotation by the skater.

The other general motion characteristic of a snow ski is its ability to offer a second direction of travel, other than the forward/backward direction. The skier can adjust their weight and rotate their body such that it causes the ski to slip forward, backward, sideways or some amount of each direction. Given that pure carving is limited to a forward component of motion; full omnidirectional motion can be achieved by the introduction of lateral motion. Lateral motion frequently is represented in the form of skidding, as when a car skids while turning on a slick surface. A snow skier can engage this second direction of travel with a velocity that is as great, or even greater than the forward motion component.

It should be noted that the aforementioned lateral, or 2^(nd) generation, direction of travel has never been available to the general roller skiing or roller skating market. Some expert roller skiers and skaters maybe able to execute a technique referred to as “power sliding”, where, through brute force alone, a rider would drive their roller ski or skate to slide sideways. This maneuver never gained wide spread popularity for several compelling reasons: (1) it was very difficult to learn and execute and thus potentially dangerous due to risk of falling; (2) it requires considerably high speeds and therefore greater risk of damaging impact forces in event of falling; (3) overcoming the considerable friction of the wheels required the users to twist their bodies very hard and place a lot of torsional stress on their knees, ankles and hips; and (4) risk of injury was also high to much of the rest of the body in the event of an failed attempt leading to a collision with the ground or other objects. Powersliding generally requires the skier to be traveling either fully sideways or not at all. All of the subtle mixtures of forward and sideways motion components, which are so compelling on snow skis, are virtually impossible to engage during a powerslide.

These determined attempts by skiers, roller skaters, roller skiers, skate boarders and snow boarders to achieve a second direction of travel are not surprising given the novel feeling of motion that it provides. Lateral sliding enables the skier to perform a wide variety of tricks and maneuvers, a snow skier can rotate 180°, 360° or more, slowly or quickly, while already in motion down a hill. A skier can land a jump in any orientation: backwards, forwards, side ways or anywhere in between—and ski away successfully. In combination with carving, lateral motion lets a skier transition in and out of skidding in a highly controlled manner to maneuver skillfully down a mountain.

Because of the great appeal of snow sports, many attempts have been made to replicate them on land and pavement. Not surprisingly, many of the prior art examples attempt to simulate skiing. Most of these devices ignore the omnidirectional mode. U.S. Pat. No. 4,134,598 to Urisaka (1979) and U.S. Pat. No. 4,805,936 to Krantz (1989) describe wheeled skis that contain a caster in conjunction with other fixed wheels. A wheeled grass ski is described in U.S. Pat. No. 5,195,781 to Osawa (1993) that simulates sidecut, theoretically enabling the device to turn when leaned to the side. U.S. Pat. No. 4,744,576 to Scollan (1988) details a device that lets the skier slide back and forth, while the device itself does not move laterally. None of these examples allow true lateral sliding with respect to the terrain being traveled over.

Amongst the prior art examples attempting to offer true lateral motion, U.S. Pat. No. 5,312,258 to Giorgio (1994) uses an array of ball-type roller bearings, unlike a snow ski or snowboard, this device includes no means for controlling the omnidirectional motion. Also, while perhaps functional on a constructed wooden “half pipe”, it would be functionally undermined by dirt and the rougher surface of pavement on a street or playground. U.S. Pat. No. 3,827,706 to Milliman (1974) uses a combination of pivoting casters and fixed casters where the fixed casters are slightly closer to the ground than the fixed wheels. This would potentially allow the skier to angle the ski in and out of a sliding mode. No means is provided to stabilize the casters or to smooth the transitions as weight is transferred from a pivoting caster to a fixed caster. U.S. Pat. No. 4,886,298 to Shols (1989) employs a complex twisting ski design that combines four casters with normal skateboard trucks. U.S. Pat No. 5,975,546 to Strand (1999) employs a snowboard inspired roller board with both feet on one platform rather than one foot on each ski.

Five patents in this area show the use of a biased, pivoting caster. U.S. Pat. No. 4,460,187 to Shimizu (1984) describes two skis bridled together with a total of only 4 fixed wheels, and U.S. Pat. No. 5,125,687 to Hwang (1992) describes a single board for simulating the parallel skiing body position. Both inventions have a single caster towards the front, with an extension spring tensioning the caster to point straight ahead. These inventions do not allow lateral sliding; they do not permit the caster to rotate through 180° or 360°; they do not allow for the possibility of multiple locations of bias on the caster; and they do not permit the characteristics of the bias force to be optimized. The skis described in U.S. Pat. No. 4,886,298 to Shols (1989) incorporates a bias via a hinge and a compliant mounting surface. As weight is applied to the ski, the caster tilts along the hinge axis, biasing the caster in the forward direction. This configuration satisfies only the ability to rotate 360° unimpeded, It does not permit more than one direction of bias; its force profile starts low and grows gradually, allowing wobbling and doing little to help the rider back into the straight ahead position; and the force profile cannot be modified. U.S. Pat. No. 5,975,546 to Strand (1999) and U.S. Pat. No. 6,419,249 to Chen (2002) incorporates bias via a spring force assisted cam system within laterally sliding roller board systems. They do not reference a ski system, nor differentiating and respectively adjustable ground clearance settings of the center platform Δhc versus front tip and rear tail planes, nor the angularity adjustability of the front tip and rear tail innovations that this present invention uncovers for further dynamic stability improvement.

Biased casters that allow unimpeded 360° rotation and specific force profiles are also described by U.S. Pat. No. 4,246,677 to Downing and Williams (1981) and U.S. Pat. No. 4,280,246 to Christensen (1981). These inventions however relate to semi-automated cart delivery systems typically used in hospitals for transporting food and medication. When the carts are lifted, the pivoting casters rotate to a predetermined angle, allowing them to move through an automated system. When the casters are touching the ground, the inventions function only to lessen wheel flutter. They are not intended to augment the cart's motion and steering characteristics.

Another distinguishing innovation of this invention from any prior art is the ground clearance and angularity adjustability of the ski. The center platform, where the skier's foot is fixtured, can be raised, lowered and rotated along the lateral center axis with respect to the ground with the use of at least one spacer and/or a bracketry system (not shown) attached between the center platform and front tip, and/or between the center platform and rear tail. These ground clearance and angularity settings can also be designed into a one piece integral ski design (not shown) that would integrate the center platform, front tip and rear tail. This innovation greatly improves the skiing experience by creating the option to lower the skier's center of gravity by bringing them self closer to the ground, thereby improving dynamic feedback when steering or controlling speed. Straight line stability can also be increased as speed increases when compared to a flat, single plane platform above the wheel assembly mounting surfaces. This innovation adds an invaluable amount critical functionality to the invention. It allows greater customization for varying application and user skill level, thereby increasing marketability and multi role usability.

Innovations have also occurred in the art of fixed wheel axle assembly design, also known as trucks. Trucks are the axle assemblies used for supporting and actuating fixed wheels on skate boards, roller skates, Strand's roller board, as well as this invention. U.S. Pat. No. 6,315,312 to Reyes, U.S. Pat. No. 6,739,603 to Powell and U.S. Pat. No. 7,413,200 to Horn all describe benefits in the application of skate boarding that may also benefit this laterally sliding ski application.

SUMMARY OF THE INVENTION

The object of this present invention is to provide a laterally sliding roller ski comprising at least one substantially rigid ski structure, for supporting at least one foot of a user, the ski structure having a central longitudinal axis and the following components:

-   -   [1] a center platform that the user stands upon;     -   [2] a front tip;     -   [3] a rear tail;     -   [4] first and second longitudinally spaced wheel assemblies         attached to the ski, each wheel assembly including:         -   [a] first and second laterally spaced fixed wheels             respectively mounted for rotation about first and second             rotational axes;         -   [b] fixed wheel mounting means attached to the front tip and             rear tail, respectively and oriented generally transversely             thereto, the fixed wheel mounting means being coupled to the             first and second fixed wheels, respectively and being             configured to maintain a first and second rotational axes of             the fixed wheels in mutually parallel relation during             steering of the ski structure, the fixed wheel mounting             means being in mechanical communication with the center             platform for steering the ski structure upon tilting of the             center platform and being biased for defining a direction of             travel along the longitudinal axis when the center platform             is in a laterally non-tilted orientation, with the center             platform extending substantially parallel, at a             longitudinally adjustable angle, with respect to a             supporting surface;         -   [c] at least two longitudinally spaced biased caster             assemblies attached to the ski structure and extending             downwardly therefrom, each caster assembly including at             least one associated roller and being mounted for pivotal             movement about a vertical axis, each caster assembly being             configured to bias the associated roller into a first and a             second pivotal position;         -   [d] the biased caster assemblies being positioned along the             central longitudinal axis, each biased caster assembly             having a lower most surface positioned lower than a lower             most surface of each of the fixed wheels;         -   [e] biased caster assembly mounting means attached to the             front tip and rear tail, respectively wherein weight of the             user is supported primarily by the biased caster assemblies             when the center platform is in the laterally non-tilted             orientation to permit movement of the ski structure in any             direction of travel;             wherein the user may selectively cause an increased portion             of their weight to be supported by one of the fixed wheels             to thereby permit steering and speed control of the roller             ski by movement of the fixed wheels relative to the center             platform upon tilting of the center platform, and wherein             each of the fixed wheels having a laterally outward directed             surface, the distance between the outwardly directed             surfaces of the first and second fixed wheels defining a             wheelbase width, the ratio of the center platform height to             the wheelbase width being less than 1.5.

Accordingly, it is the objective of the present invention to bring a new freedom of movement to roller skiing. This freedom is best represented by the motion and balance characteristics of snow skiing. Specifically, the objects and advantages are:

-   (a) to provide the ability to “carve” as a conventional roller ski     or roller skate can, where leaning weight to one side causes the     device to turn in that direction; -   (b) to provide the ability to shift into a mode of omnidirectional     behavior, where the device can easily travel forwards, backwards,     sideways or any combination thereof; -   (c) to provide the ability to transition smoothly and controllably     between carving and the omnidirectional mode; -   (d) to provide a user interface that simulates the balance     characteristics of snow skiing and other ski and roller sports,     where the omnidirectional mode is engaged when weight is relatively     evenly distributed across the skis and this mode can be exited by     transferring significant weight to the ski's edge; -   (e) to provide the ability to rotate the ski 180°, 360°, or more     repeatedly, without lifting or unweighting the ski, while in motion     over terrain; -   (f) to provide a means such that the relative ease of entering the     omnidirectional mode can be increased or decreased according to the     user's preference; -   (g) to provide the ability to ski on different types of terrain,     including paved surfaces, wood, plastic, concrete, glass, grass,     dirt, any composite blend of the aforementioned and/or even ice; -   (h) to provide a means for speed control; -   (i) to provide a means for self propulsion; -   (j) to provide a means for height and longitudinal adjustability to     change the dynamic characteristics and types of the terrain that can     be skied over; and -   (k) to create a device that is economical to produce and sell.     Further objects and advantages of my invention will become apparent     from a consideration of the drawings and ensuing description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective isometric view of the lateral sliding roller ski system of this invention in use by a skier.

FIG. 2 is a perspective bottom view of this invention.

FIG. 3 is a perspective top view of this invention.

FIG. 4 is a perspective isometric view of the fixed wheel assembly and biased caster assembly combined on a single base plate.

FIG. 5 is a perspective right side view of this invention.

FIG. 6 is a perspective front view of this invention when the skier's weight perfectly centered over the skis' longitudinal axis.

FIG. 7 is a perspective front view of the roller skis and poles when the skier's weight is shifted to their left side of the ski's longitudinal axis.

FIG. 8 is a perspective front view of the roller skis and poles when the skier's weight is shifted to their right side of the ski's longitudinal axis.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A typical embodiment of the present invention is shown in FIG. 1-4. A ski 20 has a center platform 21, two sides 22, a front tip 23, and a rear tail 24. If so desired, front tip 23 can be differ in shape from rear tail 24. Sides 22 are roughly identical to each other. Ski 20 can be wider and longer than a normal roller ski. Typical roller ski platforms measure between two to four inches wide and nineteen to twenty six inches long. Ski 20 can measure between three to eight inches wide and between thirty six to sixty inches long, depending on skier's 25 size, weight and specific application. As will be shown later, the sizing affects the trade off between maneuverability and stability.

A skier 25 positions them self on the center platform 21 in a stance similar to that used for snow skiing or conventional roller skiing, with both feet 27 roughly parallel to a longitudinal center line 29. This stance allows skier 25 to easily shift their weight from left to right or from toes to heels. Skier 25 cannot move freely about the surface of center platform 21 since they are bound to it with the use of optional snow ski style boots 26 that are fixtured within a releasable ski binding assembly 27 which restrains the toes and heels until an over powering lateral and/or torsional force overpowers the releasable ski binding 27 release spring forces. The releasable ski binding assembly 27 can be adjustable along the longitudinal center line 29 of the ski's center platform 21 for varying foot length, and skier weight—as seen with snow skis. The longitudinal center line 29 position of the entire releasable ski binding assembly 27 can also be adjusted to change the center of gravity and therefore the dynamic input and feedback experienced between the skier 25 and the ski 20. Unlike any prior art, the clearance and the angularity of the center platform 21, front tip 23 and rear tail 24 with respect to the ground can be individually adjusted with the use of at least one spacer 28 and/or a bracketry system (not shown), wedge shaped base plate spacers (not shown) under the base plates(s) 34 or by use of a one piece integral ski design (not shown) that would combine the center platform 21, front tip 23, rear tail 24 and any respective ground clearance offsets and angles in between, to once again change the dynamics of the skiing experience. The optional ground clearance and angularity settings could be permanently designed into a one piece rear ski (not shown), making it a more custom or specific application device. The one piece design could also simply be entirely flat, with the front tip 23, center platform 21 and rear tail 24 all one the same plane, thereby maximizing the ground clearance of the center platform. Regardless of height adjustability, an integral single piece design would have a better stiffness to weight ratio since the respective mating hardware junctions would be eliminated. However, if the skier 25 wishes to have a multi-piece ski 20 with ground clearance and angularity adjustability of the center platform 21, front tip 23 and/or rear tail 24, the skier 25 can adjust the trade off between straight-line/cornering stability and ground clearance needed to travel over rough and uneven surfaces. Like any ground transportation device, an increase in ground clearance directly increases the level of surface unevenness which can be traveled over, however it also drives an increase in center of gravity distance to the ground and thereby a negative result on the straight line and cornering and stopping stability and responsiveness, which is increasingly needed with speed increase. The changing in angularity of the front tip 23 and or the rear tail 24 nor use of base plate spacers has not been depicted in the figures for that sake of simplicity because the front and rear biased caster assemblies 32, front tip 23, and rear tail 24 are height adjustable already by use of the platform spacers 28 and caster height adjustment slot 52.

As shown in the FIG. 2 perspective bottom view, two basic types of mechanical components are mounted to the underside of the front tip 23 and rear tail 24. The first being fixed wheel assemblies 30 are positioned along longitudinal center line 29, one on the tip 23 and one on the tail 24, mirroring one another. Biased caster assemblies 32 can be positioned just inside of fixed wheel assemblies 30 also along longitudinal center line 29 or with their locations reversed, the fixed wheel assemblies 30 can be positioned just inside of the biased caster assemblies 32. The fixed wheel assemblies 30 provide a different functional characteristic and a different effect on maneuvering than do the biased caster assemblies 32. Fixed wheel assemblies 30 provide adjustably limited pivotal movement of fixed wheels 39 when the ski 20 is tilted and wheels 39 are contacted and pressed against the ground. Because fixed wheel assemblies 30 are oriented symmetrically such that collars 40 face towards the center of center platform 21, this pivotal movement of fixed wheels 39 causes ski 20 to turn, see FIG. 4. Thus, when the skier shifts weight laterally to one side, ski 20 turns in that direction. The fixed wheel assemblies 30 can be of the historically older technology conventionally seen on skateboards and roller skates, or one or more of the newer designs seen in the above Reyes, Powell and Horn patents for the benefits described by those inventors. Whichever fixed wheel 30 configuration is desired, the currently depicted base plate 34 for the fixed wheel assemblies 30 and biased caster assemblies 32 would need to be geometrically modified to accept the respective fixed wheel assembly prior art configuration. Each individual fixed wheel assembly 30 can be mounted on a base plate 34 that is shared with the biased caster assembly 32 or kept apart on separate base plates, see the Strand patent referred to hereinabove. Each configuration, combined or separated has it's own engineering trade off. Keeping the fixed wheel assembly 30 combined with the biased caster assembly 32 helps minimize parts count, and thereby manufacturing cost and general complexity. The base plate 34 would then also act as stiffener on the front tip 23 and rear tail 24 along the longitudinal centerline 29. Having the fixed wheel assemblies 30 and biased caster assemblies 32 on separate base plates, see the above Strand patent, allows for individual adjustment of either component along the longitudinal centerline 29 of the ski 20 and thereby allowing further modification of the dynamics of the ski 20. As shown, the biased caster assemblies 32 are combined with, and positioned as close as possible to, the fixed wheel assemblies 30 but not so close that they mechanically interfere with each other. As measured from a transverse axis 36 of one fixed wheel assembly 30 to transverse axis 36 of the other fixed wheel assembly 30, the distance can measure twenty five to sixty five inches, compared to an equivalent distance of roughly twelve to eighteen inches on a conventional roller ski. These wheel base distances can also be adjustable, by way of changing the length of the center platform 21 and/or multiple base plate 34 mounting holes 53 and/or slots on the tip 23 and tail 24 which would be oriented parallel to the longitudinal center line 29. As mentioned, the wheel base can also be changed by reversing the location of the fixed wheel assemblies 30 with the biased caster assemblies 32. In general this creates a much longer wheel base than found on a conventional roller ski. This longer wheel base makes the roller ski 20 more stable as speed increases, thereby making it easier to ski. Like wise, increasing the width of the fixed wheel assemblies 30 increases the roller ski's overall stability. It also greatly lessens the possibility of the roller ski 20 “catching an edge,” where the roller ski 20 stops abruptly while sliding laterally. The fixed wheel assemblies 30 can also measure wider than the tip and/or tail to further increase stability would mean a negative trade off of possible contact of the inside edge wheels 39. Contact could be dangerous as the wheels 39 are rotating since they can consequently slow or stop and send the skier into an unexpected turn or braking action. Finally, having the width be adjustable by way of fixed wheels 39 of various width and offset values or various truck axle mount 38 length options helps give the roller ski 20 a wide range of steering and speed control adjustability. By comparison, snow skis, conventional roller skis, surf boards, snowboards, inline skates and roller boards all become more stable as the length and width of their base and/or wheel base and wheel track is increased. The trade off is that maneuverability becomes more difficult and less sensitive, especially as speed decreases. The aforementioned optional wheel base adjustability would thereby help the skier 25 adapt to varying ski environments and conditions if so desired. The biased caster assembly 32 can also help alleviate this issue as will be described in greater detail later. In summary, the assemblies 30,32, either combined together via single base plates 34, or as shown by Strand with individual base plates, in the unique manner of this invention helps simulate snow skiing dynamics very effectively.

FIG. 3 shows a perspective top view of two ski systems 20, minus the boots 26 and skier 25. The releasable ski binding assembly 27 allows the necessary control of the ski 20 by constraining the leg, ankle and foot of the skier 25. Standing on the center platform 21 with out any leg restraint would not work unless the ski was to only travel in a straight direction—but would be uncontrollably dangerous since there would be little or no means of transferring force to the ski 20 to control speed and direction. While using a roller ski application specific permanently attached ski boot is possible, using the optional snow ski type quick release boot 26 and binding system 27 with adjustable release tension, the skier can transfer lateral and rotational forces to turn and tilt the ski 20 in order to change direction and control the speed of travel, while having the option to detach from the ski 20 in the event of an accident to attempt to avoid injury. The aforementioned releasable ski binding assembly 27 is preferable for down hill or in other words “alpine” skiing. In addition to downhill skiing, the skis can also be used for “cross country” or “telemark” skiing by changing the releasable ski binding system 27 to a cross country or telemark version, adjusting the fixed wheel assembly 30 wheelbase, respective fixed wheel 39 lateral spacing, biased caster assembly 32 wheel base, pivoting roller 45 height setting and fixed wheel assembly nut 44 torque as needed. Even the center platform 21 itself can be exchanged for an application specific alpine, cross country and telemark model. Cross country and telemark skiing often require the skier 25 to release and lift their heels off the releasable ski binding 27 in order to assist with self propulsion and the dynamic feedback experienced during turning. The optional ski poles 18 are used to balance the skier and provide traction for propulsion if need be by means of a ski pole tip 19. The pole tip 19 could be designed in a round shape as shown and preferably made of rubber, plastic, soft metal, ceramic or other material that has sufficient grip on the aforementioned desired terrains, except for ice. For ice, the tips 19 would need to be changed to a spiked or sharp edged design and preferably made of a metal, plastic, ceramic, carbon, or any composite mix of the aforementioned materials—so the ice can be sufficiently punctured for traction when supporting the weight of the skier using the poles. The releasable ski binding system 27, ski boots 26, and roller ski 20 in general, aside from pivoting rollers 45 and fixed wheels 39, can optionally be coated in abrasion/scuff resistant materials. Preferably, the materials can be a rubber, leather, plastic, metallic, ceramic based material or any combination thereof since the equipment can come in contact with asphalt, concrete, dirt, rocks, ice and other solid materials which are much more damagingly abrasive and hard on impact than typical snow. Another modification from snow skiing can be increased ventilation of the boots 26 since roller skiing can be exercised in temps far above freezing level unlike snow skiing. One boot configuration could simply look like a ski boot with cooling ventilation holes and breathable materials that resemble those seen on inline skate boots.

Referring now to FIG. 4, fixed wheel assemblies 30 can be of the conventional roller skate/skateboard design as shown. As mentioned, the fixed wheel assembly can also be of the same or similar design seen in the Reyes, Powell and/or Horn patents referred to hereinabove, and can be installed in the same orientation as the shown fixed wheel assembly 30, see FIG. 4. The conventional fixed wheel assembly 30 shown is specifically constructed as follows. A fixed wheel base 34 sandwiches an optional base plate spacer, referred to hereinabove, when attached to the front tip 23 and/or rear tail 24. The assembly has an axle mount 38 with transverse axis 36 to which a fixed wheel 39 is attached. A flexible connection is made between a collar 40 attached to axle mount 38 and base 34 with a stud 41 housed in an elastomeric sleeve 42. The sleeve 42 can preferably be made of solid or hollow rubber, urethane, silicone, or other elastomeric material including and not limited to a composite mix of the aforementioned materials. The stud 41 is restrained by a press/interference fit, threaded junction, riveted junction, weld or braze. A threaded nut 44 allows the compression of elastomeric sleeve 42 so that the force necessary for the pivotal movement can be increased or decreased. The biased caster assembly 32 provides the means for omnidirectional motion. A pivoting roller 45 stays in constant contact with the ground and can rotate to align itself with the direction of force exerted on center platform 21 while the user is turning or sliding. The biased caster assembly 32 is spring biased to align itself along longitudinal center line 29 of center platform 21, biased to point either forward or backwards, as referred to hereinabove for Chen and Strand's patents. This bias simulates the natural tracking tendency of a ski or snowboard and greatly enhances the user's stability and control. The bias is gauged to be strong enough to add control, but not so strong that the skier is impeded from rotating ski 20 into a turn or sideways travel.

In general, the spring bias is implemented as referred to hereinabove for Chen and Strand patents. Specifically, the respective pivoting roller 45 is attached to a caster 46 and rotates via a bearing assembly 48 that is housed within the base plate 34 which is attached to the underside of front tip 23 and rear tail 24, as shown in FIG. 1. The prior art figures show the different ways a cam is pivotally attached to a caster 46 and is forced by a spring as it rotates. This causes the caster 46 to rotate to a position of least force between cam and the spring. By adjusting the shape of the cam and the tension of the spring, a variety of bias profiles can be obtained, as depicted in the prior art. The prior art shows that the basic concept is that having points of least resistance allows for the caster 46 and respective pivoting roller 45 to align with the longitudinal center line 29 of the ski 20 to permit stable straight line travel and a transition of caster 46 pivoting to allow omnidirectional travel.

The roller ski of this invention succeeds because of the unique interactive effect between fixed wheel assembly 30 and biased caster assembly 32. Together, the assemblies 30,32, allow the skier to control the amount of friction between fixed wheels 39 and the surface being traveled over, whether that surface is paved asphalt, concrete, grass, dirt, rock, plastic, wood or even ice if the contacting surfaces of the pivoting rollers 45 and fixed wheels 39 were properly modified with some form of studs as seen on motorcycle and automobile tires. For ice, the fixed wheels 39 would also need the edges that contact the ground during speed control and steering to be hard, sharp and preferably made of either a metal, plastic, ceramic, carbon or composite of the aforementioned materials to provide the necessary friction to control speed and change direction. As skiers increase friction by laterally shifting weight from the pivoting rollers 45 to the fixed wheels 39, the skier 25 can carve turns. As they lessen friction by bringing more weight onto the pivoting rollers 45 along the longitudinal center line 29, fixed wheels 39, the ski 20 can slide laterally enabling the skier 25 to engage a mode of omnidirectional motion. This unique interaction of fixed wheels 39 and pivoting rollers 45 is demonstrated in FIGS. 5-8.

FIG. 5 illustrates the varying ground clearance (Δhc,Δhf,Δhr) and angularity (Δac,Δaf, Δar) between the center platform 21 Δhc/Δac, front tip 23 Δhf/Δaf and rear tail 24 Δhr/Δar, an innovative concept that is not seen in any prior art. As previously detailed, minimizing the ground clearance below the skier's foot Δhc maximizes control and user dynamic feedback thereby maximizing confidence and enjoyment in the skiing experience. Edges 22 of the center platform 21 can optionally be chamfered along their bottom edge to create greater ground clearance for deeper turning and speed control.

FIG. 6 shows two roller skis with the pivoting rollers 45 extending slightly closer to the ground than fixed wheels 39 because the skier's weight is perfectly centered over center platform 21. There are also two optional ski poles 18 shown. Ideally, all fixed wheels 39 are slightly above the ground and the skier's weight rests solely on pivoting rollers 45, in this configuration, the roller ski 20 is free to travel in any direction, constrained only by the spring (prior art) bias acting on the pivoting roller 45. It is important to note that entering the omnidirectional mode of travel does not depend on fixed wheels 39 being elevated from the ground. The important factor is the amount of force being applied to them. As long as the skier is generally centered over center platform 21, their weight will rest predominately on pivoting rollers 45. This reduces the friction between fixed wheels 39 and the ground to a level where the device can easily slide sideways.

FIG. 7 shows the positions of the front fixed wheels 39 and pivoting rollers 45 relative to the ground when the skier places their weight towards their edge of center platform 21. In this position, sufficient force can be applied to fixed wheels 39 on one side of center platform 21 to allow them to frictionally engage the ground. As a result, fixed wheels 39 prevent center platform 21 from sliding sideways. They also allow the skier 25 to carve as on a conventional roller ski or roller skate. A height differential Δhf can be measured between elevated fixed wheel 39 (on one side of center platform 21) and the ground. The greater the size of Δhf while weight is concentrated over the longitudinal center line 29 of the ski, the easier it is for the skier to enter into a mode of omnidirectional motion. By changing the height setting of the pivoting roller 45, Δhf can be increased or decreased. The value of Δhf would typically range from 1/16″ (difficult to slide laterally) to ½″ (easy to slide laterally). The height settings of the front tip pivoting roller 45, Δhf, and rear tail pivoting roller 45, Δhr, can vary from one another if the user so wishes. The height setting can be changed by repositioning the pivoting roller 45 along the caster's height adjustment slot 53, see FIG. 4, and/or base plate spacer(s) (not shown) if the base plate 34, see FIG. 2, is separate for the fixed wheel assembly 30 and biased caster assembly 32.

FIG. 8 shows the position of the front fixed wheels 39 and pivoting rollers 45 as weight is shifted to the opposite side. The effect is the same as described for FIG. 7. By shifting weight from the left edge to the right edge and vice versa, skier 25 can use the roller skis to carve without entering into a sliding mode. This behavior is equivalent to a snow skier shifting from the one edge of the skis to the other. While fixed wheels 39 frequently lose contact with the ground, the skier 25 does not feel these transitions. The actions are dampened by elastomeric sleeve 42 in fixed wheel assembly 30, and/or the other referenced prior art fixed wheel examples referred to hereinabove.

FIGS. 6-9 once again help to illustrate the width of fixed wheel assembly 30. First, the wider the axle mount 38, the smaller the proportion of weight borne by fixed wheels 39 when the skier is roughly centered on center platform 21. This minimizes friction between the fixed wheels 39 and the surface traveled over. The wider the center platform 21 and fixed wheels 39 are, up until roughly six inches, depending on rider size, skill level and desired speed, the smoother and more controllable transition between the carving mode and the omnidirectional mode.

FIGS. 6-9 also show how the skier can implement variable speed control. When the device is traveling fully sideways with the skier's weight centered over center platform 21, the travel is almost as efficient as traveling with center platform 21 pointed forward. To slow down, the skier can laterally shift their weight from the longitudinal center line 29 of the center platform 21 to left or right edge 22. This weight transfer vastly increases the friction acting on one or more of the fixed wheels 39, effectively slowing the ski. The skier 25 can vary the speed control by varying the amount of weight transfer.

As the skier 25 transitions their weight on and off of fixed wheels 39, the design of biased caster assembly 32 has many compelling advantages. First, the roller ski engages a stable position when traveling straight forward and also when traveling straight backwards. This makes it symmetrical in performance, allowing 180° rotations, just like a snow ski. Second, the bias spring force that holds the biased caster assembly 32 aligned straight limits wobbling of the pivoting roller 45 and enables the skier 25 to easily track a straight line when desired. Yet the skier can also easily rotate the skis sideways by deliberately applying force to overcome the caster spring resistance along its respective spring force profile as described in greater detail by Strand and Chen. Third, this bias is especially effective at returning the skier to a straight ahead position after executing a slide or a rotation. As the skier 25 brings the ski(s) close to straight ahead, there is a very subtle but reassuring feeling of the pivoting roller 45 locking into a forward alignment. Fourth, while the caster 46 is stable at two positions, it is free to rotate an infinite number of times unimpeded. This is especially important as snow skiers frequently seek to rotate successively in one direction. Fifth, the aforementioned bias profile can easily be modified by changing the shape of cam (prior art), the spring stiffness (prior art) or with the addition of a spring pre-load spacer (not shown). Thus, numerous custom force profiles are possible. In addition, the force profile of the front biased caster assembly 32 can be configured differently from the back biased caster assembly 32, as is the same case with the torque of the fixed wheel assembly stud threaded nut 44.

Accordingly, it can be seen that the roller ski brings a new freedom of movement to roller skiing, approximating many of the movements found in snow skiing. The roller ski provides the ability to “carve,” as a conventional roller ski can, where leaning weight to one side causes the device to turn in that direction. It permits a mode of omnidirectional motion, where the device can easily travel forwards, backwards, side-ways or any combination thereof. It provides the ability to transition smoothly and controllably between the carving mode and the omnidirectional mode.

The laterally sliding roller ski also provides a user interface that simulates the balance characteristics of snow skiing and other ski and roller sports, where the omnidirectional mode is engaged when the skier's weight is relatively evenly distributed across the skis and this mode can be exited by transferring weight to the ski's edges. It allows rotations of 180°, 360°, or more, repeatedly, without lifting or un-weighting the skis, while in motion over terrain. It includes a height and angularity adjustment means such that the relative ease of entering the omnidirectional mode can be increased or decreased according to the user's preference. The adjustability, in combination with the aforementioned material selection options, also allows provides the ability to ski on a variety of terrains, including paved asphalt, concrete, grass, dirt, rock, plastic, wood or even ice. It enables the skier 25 to propel themselves and also slow down when necessary, by increasing the friction between fixed wheels 39 and the surface traveled over. Finally the roller ski is relatively simple in its design and would be economical to produce, sell and modify for custom and general use applications.

Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given. 

1. A roller skiing device comprising: at least one substantially rigid ski structure, for supporting at least one foot of a user, the ski structure having a central longitudinal axis and the following components: [1] a center platform that the user stands upon; [2] a front tip; [3] a rear tail; [4] first and second longitudinally spaced wheel assemblies attached to the ski, each wheel assembly including: [a] first and second laterally spaced fixed wheels respectively mounted for rotation about first and second rotational axes; [b] fixed wheel mounting means attached to the front tip and rear tail, respectively and oriented generally transversely thereto, the fixed wheel mounting means being coupled to the first and second fixed wheels, respectively and being configured to maintain a first and second rotational axes of the fixed wheels in mutually parallel relation during steering of the ski structure, the fixed wheel mounting means being in mechanical communication with the center platform for steering the ski structure upon tilting of the center platform and being biased for defining a direction of travel along the longitudinal axis when the center platform is in a laterally non-tilted orientation, with the center platform extending substantially parallel, at a longitudinally adjustable angle, with respect to a supporting surface; [c] at least two longitudinally spaced biased caster assemblies attached to the ski structure and extending downwardly therefrom, each caster assembly including at least one associated roller and being mounted for pivotal movement about a vertical axis, each caster assembly being configured to bias the associated roller into a first and a second pivotal position; [d] the biased caster assemblies being positioned along the central longitudinal axis, each biased caster assembly having a lower most surface positioned lower than a lower most surface of each of the fixed wheels; [e] biased caster assembly mounting means attached to the front tip and rear tail, respectively wherein weight of the user is supported primarily by the biased caster assemblies when the center platform is in the laterally non-tilted orientation to permit movement of the ski structure in any direction of travel; wherein the user may selectively cause an increased portion of their weight to be supported by one of the fixed wheels to thereby permit steering and speed control of the roller ski by movement of the fixed wheels relative to the center platform upon tilting of the center platform, and wherein each of the fixed wheels having a laterally outward directed surface, the distance between the outwardly directed surfaces of the first and second fixed wheels defining a wheelbase width, the ratio of the center platform height to the wheelbase width being less than 1.5.
 2. The roller skiing device according to claim 1, including an abrasion resistant coating on all external surfaces.
 3. The roller skiing device according to claim 1, including at least one ventilation hole and use of breathable materials.
 4. The roller skiing device according to claim 1, including at least one detached roller ski pole held by the user comprising: [1] a substantially rigid pole structure supporting the load of a user, having a central longitudinal axis; [2] at least one of a longitudinally oriented hand grip and a wrist strap; [3] a ski pole tip located at the bottom end of the pole.
 5. The roller skiing device according to claim 1, wherein at least one of the center platform, front tip and rear tail are mounted for individual adjustability in their distance and longitudinal angle with respect to the ground.
 6. The roller skiing device according to claim 1, including at least one spacer adjacent at least one of the following elements: the center platform, front tip and rear tail, in order to accommodate at least one of the variations in distance and angle with respect to the ground and said elements.
 7. The roller skiing device according to claim 1, wherein the center platform, front tip and rear tail are configured as one integral non-adjustable ski structure.
 8. The roller skiing device according to claim 1, wherein the fixed wheel mounting means comprise at least one axle.
 9. The roller skiing device according to claim 1, wherein the first and second rotational axes are coincident.
 10. The roller skiing device according to claim 1, wherein the first and second laterally spaced fixed wheels are respectively mounted for adjustability in the distance of their respective lateral spacing;
 11. The roller skiing device according to claim 1, wherein the first and second fixed wheel assemblies are respectively mounted for adjustability in their respective longitudinal spacing;
 12. The roller skiing device according to claim 1, wherein the second pivotal position of the roller is angularly displaced by 180° from the first pivotal position.
 13. The roller skiing device according to claim 1, wherein each of the caster assemblies is configured to bias the associated roller into a first and second pivotal position.
 14. The roller skiing device according to claim 1, wherein the first and second biased caster assemblies are respectively mounted for adjustability in their longitudinal spacing.
 15. The roller skiing device according to claim 1, wherein each roller has a lowermost surface normally positioned lower than a lowermost surface of each of the fixed wheels.
 16. The roller skiing device according to claim 1, wherein the position of the lowermost surfaces of the rollers is adjustable relative to the lowermost surfaces of the fixed wheels.
 17. The roller skiing device according to claim 1, wherein the user may cause an increased portion of their body weight to be applied on the ski structure in a vector whereby it permits release from the ski structure.
 18. The roller skiing device according to claim 1, wherein the biased caster assemblies are positioned along the central longitudinal axis, with at least one caster assembly longitudinally inboard of the fixed wheels.
 19. The roller skiing device according to claim 1, wherein the biased caster assemblies are positioned along the central longitudinal axis, with at least one caster assembly outboard of the fixed wheels.
 20. The roller skiing device according to claim 1, wherein the ski structure can be adjusted to engage in at least one ski and roller sport application.
 21. The roller skiing device according to claim 1, wherein the ski structure can be adjusted to accommodate differences in weight variation and distribution.
 22. The roller skiing device according to claim 1, wherein the user can utilize a ski style boot and releasable binding system.
 23. The roller skiing device according to claim 1, wherein the user can utilize a non-releasable boot and binding system. 